[cfe-dev] Making FrontendActions composable (or not)

[Sean Silva]

On Mon, Nov 18, 2013 at 3:17 AM, Manuel Klimek <klimek at google.com> wrote:

> On Sun, Nov 17, 2013 at 11:48 AM, Sean Silva <silvas at purdue.edu> wrote:
>
>> It seems weird to be using FrontendAction for clang-tidy (and the
>> analyzer too). clang-tidy isn't a compiler frontend (I mean look at the
>> methods: hasCodeCompletionSupport? getCurrentFileKind?
>> shouldEraseOutputFiles?). AFAICT All you are really need is a vector of
>> PPCallbacks, and a vector of what is effectively
>> std::function<TidyResult(ASTContext &)>. It seems like there should be at
>> most a single FrontendAction which just sets things up so that it can
>> forward everything down into those vectors.
>>
>
> That is basically what I proposed as "b". The problem with that is that
> this is not how the static analyzer is currently factored - if I want to
> pull it apart into a PPCallbacks and an ASTConsumer, I have to duplicate
> significant amounts of code. Thus, if we want to go that way, the next step
> is to make the static analyzer more modular: basically pull out a class
> that can give you both the PPCallbacks and the ASTConsumer. But on the
> other hand, such a class already exists - it is the static analyzer's
> FrontendAction; it is exactly what we want, namely a "factory" class (well,
> in the broader sense) of a PPCallbacks and ASTConsumer instance, which
> happens to also be able to put the compiler into the state it needs it in.
>

I'm not sure I understand what you mean by "put the compiler into the state
it needs it in". That seems like it completely violates the encapsulation
(I'm imagining something like it twiddling LangOptions; that would wreak
havoc on everything else...).

-- Sean Silva


>
> Perhaps when you argue on the interface level, you mean "there should
> really be something in between a FrontendAction and an ASTConsumer or
> PPCallbacks interface", and perhaps you're right, but that sounds like a
> much bigger change...
>
> Cheers,
> /Manuel
>
>
>>
>> -- Sean Silva
>>
>>
>> On Fri, Nov 15, 2013 at 10:48 AM, Manuel Klimek <klimek at google.com>wrote:
>>
>>> Heya,
>>>
>>> while trying to integrate the static analyzer with clang-tidy I ran into
>>> the problem of combining the static analyzer's FrontendAction with
>>> clang-tidy's. As most of FrontendAction's methods are protected it is not
>>> straight forward to write a combiner/forwarder.
>>>
>>> I see multiple ways to solve this problem, but don't really know what
>>> the best way to go forward is:
>>> a) create a CombinedFrontendAction (either by befriending
>>> FrontendAction, or lowering its access boundaries); I assume that the
>>> protectedness in FrontendAction exists for a reason, so there might be
>>> downsides to this I'm not aware of
>>> b) modularize the Analyzer enough to be able to run it as a PPCallback /
>>> ASTConsumer which is registered by a one-off FrontendAction; the problem
>>> with this approach is that when we want to build higher-level tools, we
>>> always need to keep that split
>>>
>>> Thoughts?
>>> /Manuel
>>>
>>> _______________________________________________
>>> cfe-dev mailing list
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>>>
>>>
>>
>
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